Sliding vane pump using a drive shaft as a flow divider for enhanced oil circulation

ABSTRACT

A vane cell (sliding vane) pump having a flow control valve (13) with a control piston (17). The control piston (17) operates as a pressure regulator, wherein a differential pressure that occurs with increasing pump speed is used as the measuring valve for the directly diverted conveyed flow. The directly diverted conveyed flow is introduced via a spray channel (25) into a distributing section (20), which is connected via curved suction arms (21,22) with suction zones (23,24). The distributing section (20) and the suction arms (21,22) nestle against a driveshaft such that the driveshaft acts as a flow divider. Additionally, the spray channel (25) terminates at the center of the distributing section (20) so that the sprayed off oil and the suction oil conveyed by the suction channel (18) is evenly divided between both suction zones (23,24). Since the hydraulic oil lubricates the driveshaft (12), no cavitation or abrasion can occur in this area.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a vane cell pump with a cam ring seated in ahousing and a rotor with radial slits, which can be driven by means ofan input driveshaft. Work slides have been inserted into the radialslits, which sealingly slide along the cam ring. Work chambers areformed between the cam ring, the rotor and the work slides which aredelimited in the axial direction by control plates. A flow controlvalve, which on the one side is fed by the conveying pressure and on theother by the outlet pressure plus a spring force, has been installed inthe housing and can provide a connection from a pressure chamber to aspray channel connected with the suction side. In addition, a suctionchannel is divided into two symmetrically arranged curved suction armslocated in the front wall of a housing, leading to suction zones.

2. Description of the Prior Art

A vane cell pump of this type is known, for example, from U.S. Pat. No.5,112,199. This pump has two spray channels, which branch off the flowcontrol valve and are connected with the two suction zones. In addition,the suction zones are also connected via two grooves with an inlet borelocated below the flow control valve. Such a system with two sprayconduits is comparatively expensive. It is furthermore possible thatbecause of tolerances these conduits are activated in different wayswhen spraying the oil. This means that one of the two suction zones isfed only after a delay. Noise can be generated by the difference infilling of the suction zones.

Therefore the invention is based on the object of improving the pump inits spray and suction areas in such a way that an advantageous noisebehavior results even at high pump rpm, along with small manufacturingcosts.

SUMMARY OF THE INVENTION

This object is attained by the vane cell pump of the present inventionin that the suction conduit terminates in a distributing section, whichis located in the center in respect to the flow control valve and fromwhich the curved suction arms radiate, wherein the distributing sectionand the curved suction arms are arranged in such a way that the inputdriveshaft or its friction bearing bush act as flow divider. In thiscase the spray conduit of the flow control valve terminates in thecenter of the distributing section.

In accordance with the preferred embodiment, the contour of the inputdriveshaft constitutes the inner channel wall in the distributingsection and over a part of the length of the suction arms. The oildiverted in a directed manner at the flow control valve via the spraychannel into the distributing section impacts on the input driveshaftand flows on both sides of the shaft without any great resistance overthe curved suction arms into the suction zones. Since only one sprayconduit is located in the center of the distributing section, the oilcan be evenly distributed over the suction zones. The input acting as aflow divider has yet another advantage: since the oil, which is divertedin a directed manner at high speed at the flow control valve, impacts onthe input driveshaft of hard steel, no cavitation or abrasion can takeplace at this location. In case of making the channel walls of diecastmetal, of which, as a rule, the entire housing consists, such wear inthe sensitive distributing area could not be ruled out.

Practical and advantageous embodiments of the invention are describedherein. However, the invention is not limited to the combination ofcharacteristics of the invention. For one skilled in the art, furtheruseful possibilities of combining concepts and features of the inventionensue from the definition of the object.

In an alternative embodiment in accordance with the present invention, afriction bearing bush of the input driveshaft is embodied as a flowdivider, wherein the slide bearing bushing extends approximately to theinner control plate. Because the friction bearing bush is designed as atwo-component bearing, the diverted stream of the spray bore againimpacts on the hard outer steel surface of the bushing.

In accordance with another embodiment, the bore of the flow controlvalve can be inclined, starting at a pressure chamber, by approximately15° in the direction of the input driveshaft. This step results in anadvantageous spray angle and therefore an improved degree ofeffectiveness (charging) of the directedly diverted oil.

In accordance with a further embodiment, leakage oil flows from the areaof the rotor via the suction arms directly to the suction zones. Becauseof this step it is possible to omit a lubrication groove for the returnof the oil in the friction bearing of the input driveshaft.

Only one combination of the layout and application is extensivelyrepresented in the specification. It is recommended to the reader toalso consider every statement individually and to check its usefulnessin other connections and combinations, this in particular in connectionwith the cited prior art. Obvious possibilities ensue for one skilled inthe art, if the described steps are employed because of the advantagesconnected with them.

The invention will be described in detail below by means of severalexemplary embodiments, making reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Shown in:

FIG. 1, a longitudinal section through a vane cell pump in accordancewith the invention;

FIG. 2, a top view along the line II--II in FIG. 1;

FIG. 3, a partial longitudinal section through an embodiment with adriveshaft seated in a slide bearing bushing;

FIG. 4, the cross section along the line IV--IV in FIG. 3; and

FIG. 5, a partial longitudinal section through a further embodiment witha transversely arranged flow control valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Vane cell pumps are used for conveying hydraulic oil from a reservoir,not shown, to a consumer, not shown, for example a power steering.

In FIGS. 1 and 2, a rotor set 3 has been inserted in an oil filledpressure chamber 1 of a housing 2. The rotor set 3 consists of a camring 4 and a rotor 5. The rotor 5 is arranged in the interior of the camring 4 and has radially directed slits, in which vanes 6 can bedisplaced. Work chambers are formed between the cam ring, the rotor 5and the vanes 6, which are delimited in the axial direction by controlsurfaces of adjoining control plates 7 and 8. The pump corresponds to adouble-stroke embodiment.

The housing 2 is put together from a bearing housing 10 and a cup-shapedhousing cover 11. The rotor 5 is seated, fixed against relativerotation, on a driveshaft 12, which is supported in the bearing housing10. The bearing point in the bearing housing 10 is the only seating ofthe driveshaft 12. This means that the driveshaft 12 is not seated inthe radial direction in the housing cover 11. Instead, the driveshaft issupported in the axial direction on the housing cover 11.

Besides a suction connection, not shown, for connecting the reservoirand an also not shown hydraulic connection for the consumer, a flowcontrol valve 13 is provided in the bearing housing 10 for controllingthe hydraulic oil supplied to the hydraulic connector. The embodiment ofthe flow control valve 13 and of an additionally provided, but not shownpressure relief valve is generally known, for example from U.S. Pat. No.5,098,259, and will therefore not be described in detail. The hydraulicconduits which connect the work chambers with the flow control valve 13and the pressure relief valve are arranged in the bearing housing in thesame way. These conduits are also generally known and will therefore notbe described in detail.

The control plate 7 has a throttle 14 and an opening 14A. The throttleand the opening are connected with the pressure-feed work chambersformed between the rotor 5, the cam ring 4 and the vanes 6. In this casethe conveying pressure prevails in the pressure chamber 1. The conveyingpressure is supplied to the consumer via the throttle 14 and an outletchannel 19. A piston bore 15 of the flow control valve 13 axiallyadjoins the opening 14A. The piston bore 15 contains a control piston17, on which a spring 16 inserted into a spring chamber 15A acts. Thepiston bore 15 is connected with the outlet conduit 19 via a bore 27. Ascan best be seen from the top view of FIG. 2, a suction channel 18 isconnected via a distributing section 20 and two curved suction arms 21and 22 with suction zones 23 and 24. It is advantageous for the flow tolet the suction channel 18 connected to the reservoir terminate in thecenter of the distributing section 20. In a known manner the suctionzones 23 and 24 constitute the inlets of the work chambers of the pump,which are located between the vanes 6. In accordance with the invention,the distributing section 20 is centrally located under the flow controlvalve 13. The distributing section 20 and the suction arms 23 and 24 arearranged in such a way that the driveshaft 12 acts as a flow divider.Therefore the driveshaft forms a portion of the interior conduit wall. Aspray channel 25 of the flow control valve 13 terminating centrally inthe distributing section 20 is a further part of the invention. Thecontrol piston 17 of the flow control valve 13 controls the excess flowconveyed at higher rpm and directs it into the suction zones 23, 24.Since the driveshaft 12 constitutes the inner conduit wall of thedistributing section 20 and the suction arms 21, 22, a course of thechannel which is advantageous to the flow and has a good feed effect isobtained, with an even distribution of the entire suction flow. In theprocess, the stream rushing via the spray channel 25 into thedistributing section 20 drags along the oil brought through the suctionchannel 18, because of which feeding is additionally improved. In thisconnection it is advantageous if the spray channel 25 is inclined towardthe distributing section 20 (FIG. 1), so that the stream entering thespray channel 25 impacts on the driveshaft 12 made of a hard material,and not on the channel wall. It is possible by means of this to preventcavitation and abrasion in the spray channel 25. The leakage oil fromthe area of the rotor 5 can usefully be returned via the suction arms21, 22 directly to the suction zones 23, 24.

In FIGS. 3 and 4 the driveshaft 12 is supported on a friction bearingbush 26. The bush 26, which acts as a flow divider, is embodied as atwo-component bearing, i.e. the outer jacket consists of steel, forexample, while the inner surface is made of nonferrous metal. The sameadvantages result here as already mentioned in connection with FIG. 1.If a small gap "S" is left free between the face plate 7 and thefriction bearing bush 26, leakage oil again can flow through this gapfrom the area of the rotor 5 to the suction arms 21, 22 and therefore tothe suction zones 23, 24.

A further variant is represented in FIG. 5, wherein, starting at thepressure chamber 1, the piston bore 15 of the flow control valve 13 isinclined by approximately 15° in the direction toward the driveshaft 12.This step has the advantage that, when opened by the control piston 17,the piston bore is directed perpendicular or nearly perpendicular withthe spray channel 25 over a wide area, and the oil stream impacts on thecavitation-resistant driveshaft 12.

The flow control valve 13 operates as follows:

With increasing rpm the differential pressure on the front face of thecontrol piston 22 facing the opening 14A increases because of thethrottle 14. The control piston 22 acts as a pressure regulator and isdisplaced toward the left against the force of a spring 23 and the forceof the outlet pressure prevailing behind the control piston. In theprocess the front face of the control piston 22 opens the spray channel25. In this way a partial flow gets back to the inflow side of the pumpin a known manner. This results in a horizontal or descending usefulflow characteristic curve.

I claim:
 1. A vane cell pump comprising:a cam ring seated in a housing having a front wall; a rotor, which is driven by means of a driveshaft, has radial slits in which work slides are inserted that sealingly slide along the cam ring; work chambers are formed between the cam ring, the rotor and the work slides, which work chambers are delimited in the axial direction by control plates; a flow control valve, which on the one side is fed by the conveying pressure and on the other side by an outlet pressure plus a spring force, is located in the housing, which provides a connection from a pressure chamber to a spray channel; a suction channel is divided into two symmetrically arranged curved suction arms located in the front wall of the housing, leading to suction zones, the improvement comprising;the suction channel terminating in a distributing section, which is located in the center of the flow control valve, from which the curved suction arms radiate, the distributing section and the curved suction arms are being arranged in such a way that the driveshaft acts as flow divider, and the spray channel of the flow control valve terminating centrally in the distributing section.
 2. The vane cell pump in accordance with claim 1, wherein a friction bearing bush of the driveshaft acts as a flow divider and the friction bearing bush extends up to the vicinity of an inner control plate.
 3. The vane cell pump in accordance with claim 1, wherein the bore of the flow control valve, which contains a control piston, is inclined, starting at a pressure chamber, by approximately 15° in the direction of the driveshaft.
 4. The vane cell pump in accordance with claim 1, wherein leakage oil from the area of the rotor flows via the suction arms directly to the suction zones. 